That is a very impressive post, Percy, deserving of your POTM, and of course most of it I can't answer.
But I have a few overall observations and questions about it.
We have evidence that the rate of sea floor spreading has always been roughly the same. That rate is about 2-3 inches per year for the Atlantic Ocean.
The first evidence is the sedimentation depth that increases gradually from the ridge to the continent. Had the rate changed from several miles per year to several inches per year, a change of nearly a 100,000 times, then the older stretch of sea floor where the rate had been fast would have noticeably less accumulation of sediment.
I'm not following this. Presumably the continents are riding on, or riding along with, the spreading sea floor, so "the older stretch of sea floor" is the stretch closest to the continents, which is where one would expect the maximum accumulation under all circumstances. It would seem logical to me that during or right after the Flood when the continents split, at that point we might expect a lot of accumulation from the sides of the continents, no? In fact I would guess that over time the rate would slow down. I would also guess that the gradual diminishment of the depth of sediments from the continents out toward the ridge would just be the natural spreading effect of the continuously depositing sediments. I really don't see how your scenario explains anything. Doesn't demonstrate a constant rate of deposition that I can see for one thing.
You go on to say:
A creationist doesn't. In the beginning the rate may have been a few miles a year...
Keep in mind that this is a flood scenario, and that you raised it, not me. Since you raised this point I will reply to it, but I again suggest that if you do not want to discuss the flood scenario that you stop using it in your arguments.
That's fine. I acknowledge that I raised it and if I raised it before and forgot, I apologize.
If the sea floor had been moving at, let us say, 3 miles per year from 5000 years ago until 2000 years ago, and then after that at the rate of 3 inches per year, then sea floor that is 5000 years old would now be a distance of 1500 miles from the ridge on each side, and sea floor that is 2000 years old would be a distance of about a mile from the ridge. In other words, most of the ocean floor would be less than 5000 years old, because the continents aren't much more than 1500 miles from the ridge.
Yes, that's true (although from a flood perspective a gradual slowing is what would have been expected from the start of it.)
Given the sedimentation accumulation rate of about a centimeter per century, it would mean that the sea floor that is about 1500 miles from the ridge should have a depth of sedimentation of about a yard or two. What is the actual depth of sediment at that distance? A mile or two. That's because sediment has been raining on the sea floor at the centimeter per century rate for millions of years.
Or because there was very fast accumulation for some period just after the continents split, and a higher rate than you posit all along, although gradually slowing down over the last 5000 years. You don't know the rate of accumulation. You said it was known, but how can it be known? All you can know is the rate NOW. But I see you will go on to discuss this further.
Confirming evidence that the rate of sea floor spreading has always been slow is sea floor striping. This is where the sea floor produced at mid-oceanic ridges acquires a weak magnetic field in the same direction as the earth's magnetic field while it is cooling. I know the creationist response to this, but you said you didn't want to discuss the flood scenario, so if you don't introduce the creationist argument then neither will I. But we know with pretty great certainty that new sea floor has to cool before it can acquire a magnetic field (if you heat a magnet, it loses its magnetism), and that the magnetic field of the earth is locked in during the cooling process by being exposed to the earth's magnetic field over a relatively long stretch of time. New sea floor can only cool so fast, and so it takes time to acquire and lock in a magnetic field.
We also theorize that the earth's magnetic field is due to processes in the earth's outer core that are poorly understood at this time, but we do understand that it takes a considerable time for billions of tons of material to change their flow patterns. The earth's magnetic field reverses itself on average every half million years or so.
Well, I'm aware of the magnetic striping but not up on the arguments, and although yours may be quite logical I'm sure the creationists' is too, so I hope you won't mind if I simply reserve this one for some other time.
Radiometric dating is what gives sedimentation, sea floor spreading, magnetic sea floor striping and magnetic field reversals their absolute timescale. All applicable radiometric techniques agree that the sea floor of the Atlantic Ocean closest to the continents is millions and millions of years old. Radiometric dating tells us that the deepest sediments on the sea floor are also millions and millions of years old. Radiometric dates for sedimentary layers in the Atlantic Ocean correlate with the radiometric dates for the equivalent layers in all the other oceans.
At any rate of sedimentation over such supposed millions and millions of years, there shouldn't be any land mass left at all I would think; it should all have dissolved into the oceans.
So now you are going to go on to the layering of the sedimentation, and I just want to orient myself: didn't this originally come up as an answer to my "incredulity" about how the geo column could have formed? Depth of sediment you can show, but you have to show the different layers of different sediments, not to mention different fossil contents, which it appears you can answer in the following, but then there's also the question if you are expecting the sea floor to accumulate sediments periodically and then rise to form land mass, in order to account for the geo column effect? How feasible is the idea that much of the existing geo column was formed by rising ocean deposits like this?
The same is true for the magnetic field reversals. A sedimentary layer in the Atlantic ocean that is dated to 20 million years old will have the same magnetic field direction as a sedimentary layer from the Pacific ocean that is also dates to 20 million years old. So you can see that we don't just assume the rate of sea floor spreading has always been the same. There is so much evidence for a relatively constant and slow rate that even if we didn't want to accept it, we'd pretty much be forced to.
I get your reasoning more or less.
But can you account for the LAYERS this way, the COMPLETELY DIFFERENT SEDIMENTS involved with their COMPLETELY DIFFERENT fossil contents?
Yes, of course. Ocean sediments far from coastlines are a reflection of the ocean life that lives above the sea floor and upon it. Areas of the ocean with a thriving ecology will accumulate sediments with high organic content, which would be limestone. Warm shallow seas are most noted for producing calcium carbonate rich deposits that will eventually become limestone.
An area of ocean that is receiving calcium carbonate rich sedimentary deposits and then is uplifted (but still under water) and finds itself not too far from a continental coast will begin to experience increased mud and silt that is delivered to the oceans by rivers and streams and from run-off. Though the calcium carbonate is still present, the mud and silt begins to dominate and now a sedimentary layer is forming that will eventually become a layer of shale.
As this area of ocean continues to uplift and becomes closer to the shoreline the heavier sand from rivers, streams and coastal runoff begins to dominate in the sediments deposited on the sea floor. The lighter mud and silt stays in suspension near the coastline and won't fall out of suspension until further from shore where it forms shale deposits, but the area of ocean we're considering is now right next to the coast and is receiving predominantly sand. The detritus from continents delivered into the oceans is immense, and sea floor near coastlines accumulates sediments at nearly five times the rate far out to sea.
So you think that horizontal layers can be formed (and preserved in their horizontal state) through periodic "uplifting" of the ocean floor. How often does such uplifting occur in actuality -- is it known or merely hypothesized to occur? -- and by what means, and wouldn't there be more apparent graduation (mixing of sediments) in the layers to the naked eye than we see in the geo column if this is how it formed?
This is all interesting, however, and makes me wonder about similar processes in the Flood.
Depending upon the ecology on and above the sea floor, the sediments also accumulate a record of the local sea life resident at the time. Some of the sea life is bottom dwellers, some are swimmers. Some are large, but many are microscopic. The changing life forms found in the layers are a record of both migration and evolution, but the older the sedimentary layer the more different those life forms are from modern life.
That's logical. However, shouldn't the layers beneath the sea reflect the same existent geo column that is now considered to reflect the great ages of the earth? It sounds like you are describing a more recent accumulation of material rather than something that parallels the supposed ages of the column. Where are the time periods in these layers under the sea? How old are the sediments according to the OE understanding? Shouldn't those farthest from the ridge (closest to the continents) reflect whatever period is normally dated to the age of those?
Then is it your theory that the sea floor periodically rises to the surface and forms new land? Wouldn't that make an awful LOT of the present land former sea floor? Is that the theory?
Marine sedimentary layers are found in many places around the world. By examining the sediments we can tell that except for being compressed and lithified into rock they are just like the limestone, shale or sandstone layers we can see being deposited in modern oceans today.
When we see marine layers on land we know that they used to be sea floor and that the area was submerged at one time and then uplifted. Or possibly the ocean levels fell, or possibly a combination. Remember that limestone layers form far from shore, shale layers closer to shore, and sandstone layers very near or at the shore. When we see repeated patterns of limestone, shale and sandstone layers we know that the area has gone through repeated periods of being far from shore, closer to shore, and very near or at the shore. By dating the layers you can actually reproduce and map how an ancient shoreline moved back and forth across a landscape.
I'd like to see such a map. But again this suggests massive shifting between or reversals of what used to be ocean floor and what used to be land mass.
That does seem to be the way most of the layers are thought to have formed. Mountainbuilding on the land is another but how much is thought to have come from that source, and again, does it exhibit the layering of different sediments and different fossil contents?
Mountain building does not create layers.
Well I believe it was roxrkool who said it does, so I will leave that to her or whoever said something along those lines.
It can only lift up and elevate layers. In the Alps and Himalayas you can find marine deposits on mountain peaks. And since mountains are the most exposed geologic forms on the landscape, they are also the most quickly eroded. Twenty or thirty million years is all it takes to erode a mountain range the size of the Alps to nubs (assuming uplift is no longer present - the Himilayas are being eroded at a fair clip, but they're being uplifted even faster), and all the sedimentary layers that filled them flow back to the oceans in rivers, streams and continental run-off.
But LAYERS is what we want to see.
And how do the depths of the present-forming sediments in either case compare with those {ABE: OF THE LAYERS} in the geo column, including the ideas of course about how {ABE: THE LAYERS} in the geo column may in fact have been originally much much thicker than they now are?
You're asking a question about a point you were discussing with someone else. I'm not quite certain of the point the other person was trying to make, so let me describe this in my own way.
An unconformity is a boundary between two adjacent geological layers where the lower layer was eroded away to some degree before the upper layer was deposited.
And there may not be any actual physical evidence of erosion, or merely minimal signs of such erosion -- this is really mostly just the idea that this other layer "should" have been there according to the idea about the ages of the geo column, isn't it?
An example of this happening would be a shoreline area with deep standstone deposits, lets say a couple hundred feet or so. A combination of a drop in ocean level and an uplift of the area leaves this layer a couple hundred feet above sea level, and erosion removes a hundred feet of the sandstone, which isn't really hard sandstone yet since it hasn't ever been deeply buried and so has never had too great a weight upon it. Even so, it will take a considerable period to erode away a hundred feet of soft sandstone because the top quickly acquires a layer of dirt and then of flora which protect it.
Maybe it takes a couple hundred thousand years to erode away a hundred feet of sandstone, and then rising ocean levels and/or subsidence sink the area once again beneath the waves. This is a substantial drop this time, and the area finds itself far from shore and a thousand feet below sea level. Suddenly our sandstone is beneath a shallow sea, and very shortly a rain of calcium carbonate begins from the skeletons of microscopic creatures living and dying in the waters above. A limestone layer begins to form atop the sandstone.
One thing you might be able to tell from this scenario is that we can't really know how much sandstone was eroded away. I said a hundred feet in my example, but what if only a foot of standstone had been eroded way, or what if hundreds of feet of sandstone had been eroded away. We can't know how much because it is no longer there. If we come back as junior geologists millions of years later, we can see the uncomformity between the sandstone layer and limestone layer just above it, but the material that was eroded away is nowhere to be found. We can't know how much sandstone used to lie above the unconformity boundary.
Sometimes we do know how much was eroded away because the same layer exists some distance away where it was never uplifted above sea level and so was never eroded away. I don't really know how often this is the case.
So an unconformity tells us that material has been eroded away, but it doesn't tell us how much. It could have been a foot of material, it could have been thousands of feet of material.
To answer your question about how well the layers found in the geological column correspond to contemporary layers forming today, the answer is that except that they've been compressed and lithified into rock, they're identical. Of course there are differences in fossil types according to age and geographical region, and there can be mineral differences due to local or special circumstances in some layers, like the high iron oxide content of layers thought to correspond to when oxygen became a significant presence in the atmosphere, but otherwise the limestone, shale and sandstone layers forming today are identical to those of yesteryear.
OK I'll just leave all this as it is just too much to think through. Thanks for your time.
™ Version 4.2